This invention relates to epitaxial growing apparatus for growing an epitaxial thin film layer of a semiconductor substance on a substrate mounted on a support member (suscepta) which is heated by high frequency energy or infrared radiation ray in a gas-tight reaction chamber, and more particularly, an improved construction of a base plate and a bell jar which define a gas-tight reaction chamber of an epitaxial growing apparatus.
Typical conventional epitaxial growing apparatus are shown in FIGS. 1 and 2, which particularly represent vertical type (so-called pancake type) epitaxial growing apparatus. Referring to FIG. 1, a bell jar 3 made of quartz (quartz bell jar, called hereinbelow) is mounted on a base plate 1, which generally comprises a stainless steel plate, through a seal member 2 such as an O-ring. The quartz bell jar 3 and the base plate 1 define a gas-tight reaction chamber 4 therebetween, in which a nozzle member 7 extends vertically through the base plate 1 and a support member 5 on which substrates 6 are mounted is rotatably arranged around the nozzle 7. The support member 5 is heated by a high frequency induction heating coil 8 located below the support member 5 and gas exhaust pipes 9 are connected to the base plate 1. A clean bench 10 is located to surround the epitaxial growing apparatus. Since the reaction chamber 4 is defined by the bell jar 3 made of quartz, radiant heat from the support member 5 is dispersed outwardly through the quartz bell jar 3, so that a good thermal efficiency cannot be attained and the dispersed heat is dangerous for workers. In addition, the quartz bell jar 3 is itself apt to be easily broken by an accidental external impact.
Moreover, with the conventional epitaxial growing apparatus of the type described above, it is obliged to cool the side panel of the clean bench 10 arranged to surround the apparatus for the purpose that the clean bench 10 is heated to a relatively high temperature by the radiant heat through the quartz bell jar 3.
FIG. 2 also shows a conventional epitaxial growing apparatus in which a stainless steel made bell jar 11 is mounted on the base plate 1. A quartz bell jar 14 is located inside the stainless steel bell jar 11 and supported by a plurality of (preferably more than three) screw type support pieces 13 secured to the lower peripheral end of the stainless steel bell jar 11 (FIG. 2a) and cooling pipes 12 are arranged on the outer surface of the stainless steel bell jar 11 to prevent the radiant heat from dispersing outwardly of the stainless steel bell jar 11. Thus, the defects of the epitaxial growing apparatus shown in FIG. 1 could be obviated by the apparatus shown in FIG. 2. However, with the epitaxial growing apparatus shown in FIG. 2, since a space between the quartz bell jar 14 and the stainless steel bell jar 11 communicates with the reaction chamber 4, because the former bell jar 14 is supported at several portions to the latter bell jar 11 by the support pieces 13, a reaction gas supplied in the chamber 4 from the nozzle 7 flows into this space, thus forming undesired reaction substances therein. In order to avoid this defect, the stainless steel bell jar 11 is provided with a port 15 through which a purge gas such as hydrogen gas with high purity should be supplied in the space during the operation of the epitaxial growing apparatus. Thus, the conventional epitaxial growing apparatus shown in FIG. 2 will also be considered not to be a satisfied apparatus.